In recent years, flat panel displays have been utilized in various products and fields, and there are demands for flat panel displays having even larger sizes, even higher picture quality, and even lower power consumption.
In view of such circumstances, organic electroluminescence (referred to as EL below) display devices provided with organic EL elements utilizing the electro luminescence of organic materials are attracting much attention as flat panel displays due to their excellent qualities, such as low voltage driving, high responsiveness, and self-luminosity, while being in a completely solid state.
For example, in the case of an active-matrix organic EL display device, a thin-filmed organic EL element is disposed on a substrate on which thin film transistors (TFT) are provided. The organic EL element includes an organic EL layer including a light-emitting layer layered between a pair of electrodes. The TFT is connected with either side of the pair of electrodes. Then, voltage is applied across the pair of electrodes to make the light-emitting layer emit light, whereby image display is performed.
Additionally, in the known organic EL display device as described above, in order to configure a device capable of being repeatedly bent (being bendable), it is known that a base material having flexibility is used as a support substrate for supporting the above-described organic EL element.
Furthermore, the known organic EL display device as described above, as disclosed in PTL 1 indicated below, for example, includes a base material having flexibility and an organic EL element fixed on this base material. Additionally, in this known organic EL display device, it is proposed to fix a cover layer having flexibility on the organic EL element, and to set a Young's modulus and a thickness of the cover layer such that a neutral surface of the organic EL display device is positioned in the vicinity of the organic EL element. Additionally, it is stated that, in this known organic EL display device, even in a case where the organic EL display device is bent, it is possible to suppress distortion or the like of the organic EL element from occurring and to prevent reliability from being reduced.